Right now, we send the tgid cross the wire. What we really want to send
though is a hashed fl_owner_t since samba treats this field as a generic
lockowner.

It turns out that because we enforce and release locks locally before
they are ever sent to the server, this patch makes no difference in
behavior. Still, setting OFD locks on the server using the process
pid seems wrong, so I think this patch still makes sense.
Signed-off-by: NJeff Layton <jlayton@poochiereds.net>
Signed-off-by: NSteve French <smfrench@gmail.com>
Acked-by: NPavel Shilovsky <pshilovsky@samba.org>
Acked-by: NSachin Prabhu <sprabhu@redhat.com>

Check for d_unhashed() while searching in in-lookup hash was absolutely
wrong.  Worse, it masked a deadlock on dget() done under bitlock that
nests inside ->d_lock.  Thanks to J. R. Okajima for spotting it.
Spotted-by: N"J. R. Okajima" <hooanon05g@gmail.com>
Wearing-brown-paperbag: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Older btrfs-progs/mkfs.btrfs sets 4096 as the stripesize. Hence
restricting stripesize to be equal to sectorsize would cause super block
validation to return an error on architectures where PAGE_SIZE is not
equal to 4096.

Hence as a workaround, this commit allows stripesize to be set to 4096
bytes.
Signed-off-by: NChandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Introduced in 2c1984f2 ("btrfs: build fixup for
qgroup_account_snapshot") as temporary bisectability build fixup.
Signed-off-by: NDavid Sterba <dsterba@suse.com>

We've renamed btrfs_std_error, this one is left from last merge.
Signed-off-by: NDavid Sterba <dsterba@suse.com>

This fixes a problem introduced in commit 2f3165ec
"btrfs: don't force mounts to wait for cleaner_kthread to delete one or more subvolumes".

open_ctree eventually calls btrfs_replay_log which in turn calls
btrfs_commit_super which tries to lock the cleaner_mutex, causing a
recursive mutex deadlock during mount.

Instead of playing whack-a-mole trying to keep up with all the
functions that may want to lock cleaner_mutex, put all the cleaner_mutex
lockers back where they were, and attack the problem more directly:
keep cleaner_kthread asleep until the filesystem is mounted.

When filesystems are mounted read-only and later remounted read-write,
open_ctree did not set fs_info->open and neither does anything else.
Set this flag in btrfs_remount so that neither btrfs_delete_unused_bgs
nor cleaner_kthread get confused by the common case of "/" filesystem
read-only mount followed by read-write remount.
Signed-off-by: NZygo Blaxell <ce3g8jdj@umail.furryterror.org>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

This is just a screwup for developers, so change it to an ASSERT() so developers
notice when things go wrong and deal with the error appropriately if ASSERT()
isn't enabled.  Thanks,
Signed-off-by: NJosef Bacik <jbacik@fb.com>
Reviewed-by: NMark Fasheh <mfasheh@suse.de>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The test for !trans->blocks_used in btrfs_abort_transaction is
insufficient to determine whether it's safe to drop the transaction
handle on the floor.  btrfs_cow_block, informed by should_cow_block,
can return blocks that have already been CoW'd in the current
transaction.  trans->blocks_used is only incremented for new block
allocations. If an operation overlaps the blocks in the current
transaction entirely and must abort the transaction, we'll happily
let it clean up the trans handle even though it may have modified
the blocks and will commit an incomplete operation.

In the long-term, I'd like to do closer tracking of when the fs
is actually modified so we can still recover as gracefully as possible,
but that approach will need some discussion.  In the short term,
since this is the only code using trans->blocks_used, let's just
switch it to a bool indicating whether any blocks were used and set
it when should_cow_block returns false.

Cc: stable@vger.kernel.org # 3.4+
Signed-off-by: NJeff Mahoney <jeffm@suse.com>
Reviewed-by: NFilipe Manana <fdmanana@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Thanks to fuzz testing, we can pass an invalid bytenr to extent buffer
via alloc_extent_buffer().  An unaligned eb can have more pages than it
should have, which ends up extent buffer's leak or some corrupted content
in extent buffer.

This adds a warning to let us quickly know what was happening.

Now that alloc_extent_buffer() no more returns NULL, this changes its
caller and callers of its caller to match with the new error
handling.
Signed-off-by: NLiu Bo <bo.li.liu@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Component mirror_num of struct btrfsic_block is defined
as unsigned int. Use %u as format specifier.
Signed-off-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Move the state selection logic inside from the caller,
always making it return correct stp to use.
Signed-off-by: NJ . Bruce Fields <bfields@fieldses.org>
Signed-off-by: NOleg Drokin <green@linuxhacker.ru>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

To avoid racing entry into nfs4_get_vfs_file().
Make init_open_stateid() return with locked stateid to be unlocked
by the caller.
Signed-off-by: NOleg Drokin <green@linuxhacker.ru>
Cc: stable@vger.kernel.org
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

It used to be the case that state had an rwlock that was locked for write
by downgrades, but for read for upgrades (opens). Well, the problem is
if there are two competing opens for the same state, they step on
each other toes potentially leading to leaking file descriptors
from the state structure, since access mode is a bitmap only set once.
Signed-off-by: NOleg Drokin <green@linuxhacker.ru>
Cc: stable@vger.kernel.org
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

Also simplify the logic a bit.

Cc: stable@vger.kernel.org
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>
Acked-by: NTrond Myklebust <trondmy@primarydata.com>

Fix a regression when creating a file over a whiteout.  The new
file/directory needs to use the current fsuid/fsgid, not the ones from the
mounter's credentials.

The refcounting is a bit tricky: prepare_creds() sets an original refcount,
override_creds() gets one more, which revert_cred() drops.  So

  1) we need to expicitly put the mounter's credentials when overriding
     with the updated one

  2) we need to put the original ref to the updated creds (and this can
     safely be done before revert_creds(), since we'll still have the ref
     from override_creds()).
Reported-by: NStephen Smalley <sds@tycho.nsa.gov>
Fixes: 3fe6e52f ("ovl: override creds with the ones from the superblock mounter")
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Debugfs' open_proxy_open(), the ->open() installed at all inodes created
through debugfs_create_file_unsafe(),
- grabs a reference to the original file_operations instance passed to
  debugfs_create_file_unsafe() via fops_get(),
- installs it at the file's ->f_op by means of replace_fops()
- and calls fops_put() on it.

Since the semantics of replace_fops() are such that the reference's
ownership is transferred, the subsequent fops_put() will result in a double
release when the file is eventually closed.

Currently, this is not an issue since fops_put() basically does a
module_put() on the file_operations' ->owner only and there don't exist any
modules calling debugfs_create_file_unsafe() yet. This is expected to
change in the future though, c.f. commit c6468808 ("debugfs: add
support for self-protecting attribute file fops").

Remove the call to fops_put() from open_proxy_open().

Fixes: 9fd4dcec ("debugfs: prevent access to possibly dead
                      file_operations at file open")
Signed-off-by: NNicolai Stange <nicstange@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Debugfs' full_proxy_open(), the ->open() installed at all inodes created
through debugfs_create_file(),
- grabs a reference to the original struct file_operations instance passed
  to debugfs_create_file(),
- dynamically allocates a proxy struct file_operations instance wrapping
  the original
- and installs this at the file's ->f_op.

Afterwards, it calls the original ->open() and passes its return value back
to the VFS layer.

Now, if that return value indicates failure, the VFS layer won't ever call
->release() and thus, neither the reference to the original file_operations
nor the memory for the proxy file_operations will get released, i.e. both
are leaked.

Upon failure of the original fops' ->open(), undo the proxy installation.
That is:
- Set the struct file ->f_op to what it had been when full_proxy_open()
  was entered.
- Drop the reference to the original file_operations.
- Free the memory holding the proxy file_operations.

Fixes: 49d200de ("debugfs: prevent access to removed files' private
                      data")
Signed-off-by: NNicolai Stange <nicstange@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

In rare cases it is possible for s_flags & MS_RDONLY to be set but
MNT_READONLY to be clear.  This starting combination can cause
fs_fully_visible to fail to ensure that the new mount is readonly.
Therefore force MNT_LOCK_READONLY in the new mount if MS_RDONLY
is set on the source filesystem of the mount.

In general both MS_RDONLY and MNT_READONLY are set at the same for
mounts so I don't expect any programs to care.  Nor do I expect
MS_RDONLY to be set on proc or sysfs in the initial user namespace,
which further decreases the likelyhood of problems.

Which means this change should only affect system configurations by
paranoid sysadmins who should welcome the additional protection
as it keeps people from wriggling out of their policies.

Cc: stable@vger.kernel.org
Fixes: 8c6cf9cc ("mnt: Modify fs_fully_visible to deal with locked ro nodev and atime")
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

On 32-bit:

    fs/nfsd/blocklayout.c: In function ‘nfsd4_block_get_device_info_scsi’:
    fs/nfsd/blocklayout.c:337: warning: integer constant is too large for ‘long’ type
    fs/nfsd/blocklayout.c:344: warning: integer constant is too large for ‘long’ type
    fs/nfsd/blocklayout.c: In function ‘nfsd4_scsi_fence_client’:
    fs/nfsd/blocklayout.c:385: warning: integer constant is too large for ‘long’ type

Add the missing "ULL" postfix to 64-bit constant NFSD_MDS_PR_KEY to fix
this.

Fixes: f99d4fbd ("nfsd: add SCSI layout support")
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

* make autofs4_expire_indirect() skip the dentries being in process of
expiry
* do *not* mess with list_move(); making sure that dentry with
AUTOFS_INF_EXPIRING are not picked for expiry is enough.
* do not remove NO_RCU when we set EXPIRING, don't bother with smp_mb()
there.  Clear it at the same time we clear EXPIRING.  Makes a bunch of
tests simpler.
* rename NO_RCU to WANT_EXPIRE, which is what it really is.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

This prevents users from triggering a stack overflow through a recursive
invocation of pagefault handling that involves mapping procfs files into
virtual memory.
Signed-off-by: NJann Horn <jannh@google.com>
Acked-by: NTyler Hicks <tyhicks@canonical.com>
Cc: stable@vger.kernel.org
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This prevents stacking filesystems (ecryptfs and overlayfs) from using
procfs as lower filesystem.  There is too much magic going on inside
procfs, and there is no good reason to stack stuff on top of procfs.

(For example, procfs does access checks in VFS open handlers, and
ecryptfs by design calls open handlers from a kernel thread that doesn't
drop privileges or so.)
Signed-off-by: NJann Horn <jannh@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

d_walk() relies upon the tree not getting rearranged under it without
rename_lock being touched.  And we do grab rename_lock around the
places that change the tree topology.  Unfortunately, branch reordering
is just as bad from d_walk() POV and we have two places that do it
without touching rename_lock - one in handling of cursors (for ramfs-style
directories) and another in autofs.  autofs one is a separate story; this
commit deals with the cursors.
	* mark cursor dentries explicitly at allocation time
	* make __dentry_kill() leave ->d_child.next pointing to the next
non-cursor sibling, making sure that it won't be moved around unnoticed
before the parent is relocked on ascend-to-parent path in d_walk().
	* make d_walk() skip cursors explicitly; strictly speaking it's
not necessary (all callbacks we pass to d_walk() are no-ops on cursors),
but it makes analysis easier.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

The offset in the core file used to be tracked with ->written field of
the coredump_params structure. The field was retired in favour of
file->f_pos.

However, ->f_pos is not maintained for pipes which leads to breakage.

Restore explicit tracking of the offset in coredump_params. Introduce
->pos field for this purpose since ->written was already reused.

Fixes: a0083939 ("get rid of coredump_params->written").
Reported-by: NZbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Signed-off-by: NMateusz Guzik <mguzik@redhat.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

open("/foo/no_such_file", O_RDONLY | O_CREAT) on should fail with
EACCES when /foo is not writable; failing with ENOENT is obviously
wrong.  That got broken by a braino introduced when moving the
creat_error logics from atomic_open() to lookup_open().  Easy to
fix, fortunately.
Spotted-by: N"Yan, Zheng" <ukernel@gmail.com>
Tested-by: N"Yan, Zheng" <ukernel@gmail.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Ascend-to-parent logics in d_walk() depends on all encountered child
dentries not getting freed without an RCU delay.  Unfortunately, in
quite a few cases it is not true, with hard-to-hit oopsable race as
the result.

Fortunately, the fix is simiple; right now the rule is "if it ever
been hashed, freeing must be delayed" and changing it to "if it
ever had a parent, freeing must be delayed" closes that hole and
covers all cases the old rule used to cover.  Moreover, pipes and
sockets remain _not_ covered, so we do not introduce RCU delay in
the cases which are the reason for having that delay conditional
in the first place.

Cc: stable@vger.kernel.org # v3.2+ (and watch out for __d_materialise_dentry())
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

MNT_LOCKED implies on a child mount implies the child is locked to the
parent.  So while looping through the children the children should be
tested (not their parent).

Typically an unshare of a mount namespace locks all mounts together
making both the parent and the slave as locked but there are a few
corner cases where other things work.

Cc: stable@vger.kernel.org
Fixes: ceeb0e5d ("vfs: Ignore unlocked mounts in fs_fully_visible")
Reported-by: NSeth Forshee <seth.forshee@canonical.com>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Add this trivial missing error handling.

Cc: stable@vger.kernel.org
Fixes: 1b852bce ("mnt: Refactor the logic for mounting sysfs and proc in a user namespace")
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

In __test_eb_bitmaps(), we write random data to a bitmap. Then copy
the bitmap to another bitmap that resides inside an extent buffer.
Later we verify the values of corresponding bits in the bitmap and the
bitmap inside the extent buffer. However, extent_buffer_test_bit()
reads in byte granularity while test_bit() reads in unsigned long
granularity. Hence we end up comparing wrong bits on big-endian
systems such as ppc64. This commit fixes the issue by reading the
bitmap in byte granularity.
Reviewed-by: NJosef Bacik <jbacik@fb.com>
Reviewed-by: NChandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: NFeifei Xu <xufeifei@linux.vnet.ibm.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

With 64K sectorsize, 1G sized block group cannot span across bitmaps.
To execute test_bitmaps() function, this commit allocates
"BITS_PER_BITMAP * sectorsize + PAGE_SIZE" sized block group.
Reviewed-by: NJosef Bacik <jbacik@fb.com>
Reviewed-by: NChandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: NFeifei Xu <xufeifei@linux.vnet.ibm.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

This commit replaces numerical constants with appropriate
preprocessor macros.
Reviewed-by: NJosef Bacik <jbacik@fb.com>
Signed-off-by: NChandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: NFeifei Xu <xufeifei@linux.vnet.ibm.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

To test all possible sectorsizes, this commit adds a sectorsize
array. This commit executes the tests for all possible sectorsizes and
nodesizes.
Reviewed-by: NJosef Bacik <jbacik@fb.com>
Signed-off-by: NChandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: NFeifei Xu <xufeifei@linux.vnet.ibm.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

On ppc64, PAGE_SIZE is 64k which is same as BTRFS_MAX_METADATA_BLOCKSIZE.
In such a scenario, we will never be able to have an extent buffer
containing more than one page. Hence in such cases this commit does not
execute the page straddling tests.
Reviewed-by: NJosef Bacik <jbacik@fb.com>
Signed-off-by: NFeifei Xu <xufeifei@linux.vnet.ibm.com>
Signed-off-by: NChandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

a) ovl_need_xattr_filter() is wrong, we can have multiple lower layers
overlaid, all of which (except the lowest one) honouring the
"trusted.overlay.opaque" xattr.  So need to filter everything except the
bottom and the pure-upper layer.

b) we no longer can assume that inode is attached to dentry in
get/setxattr.

This patch unconditionally filters private xattrs to fix both of the above.
Performance impact for get/removexattrs is likely in the noise.

For listxattrs it might be measurable in pathological cases, but I very
much hope nobody cares.  If they do, we'll fix it then.
Reported-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>
Fixes: b9680917 ("security_d_instantiate(): move to the point prior to attaching dentry to inode")

Since several architectures support hardware-accelerated crc32c
calculation, it would be nice to confirm that btrfs is actually using it.

We can see an elevated use count for the module, but it doesn't actually
show who the users are.  This patch simply prints the name of the driver
after successfully initializing the shash.
Signed-off-by: NJeff Mahoney <jeffm@suse.com>
[ added a helper and used in module load-time message ]
Signed-off-by: NDavid Sterba <dsterba@suse.com>

To prevent fuzzed filesystem images from panic the whole system,
we need various validation checks to refuse to mount such an image
if btrfs finds any invalid value during loading chunks, including
both sys_array and regular chunks.

Note that these checks may not be sufficient to cover all corner cases,
feel free to add more checks.
Reported-by: NVegard Nossum <vegard.nossum@oracle.com>
Reported-by: NQuentin Casasnovas <quentin.casasnovas@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

This adds validation checks for super_total_bytes, super_bytes_used and
super_stripesize, super_num_devices.
Reported-by: NVegard Nossum <vegard.nossum@oracle.com>
Reported-by: NQuentin Casasnovas <quentin.casasnovas@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

We set uptodate flag to pages in the temporary sys_array eb,
but do not clear the flag after free eb.  As the special
btree inode may still hold a reference on those pages, the
uptodate flag can remain alive in them.

If btrfs_super_chunk_root has been intentionally changed to the
offset of this sys_array eb, reading chunk_root will read content
of sys_array and it will skip our beautiful checks in
btree_readpage_end_io_hook() because of
"pages of eb are uptodate => eb is uptodate"

This adds the 'clear uptodate' part to force it to read from disk.
Reviewed-by: NJosef Bacik <jbacik@fb.com>
Signed-off-by: NLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The /dev/ptmx device node is changed to lookup the directory entry "pts"
in the same directory as the /dev/ptmx device node was opened in.  If
there is a "pts" entry and that entry is a devpts filesystem /dev/ptmx
uses that filesystem.  Otherwise the open of /dev/ptmx fails.

The DEVPTS_MULTIPLE_INSTANCES configuration option is removed, so that
userspace can now safely depend on each mount of devpts creating a new
instance of the filesystem.

Each mount of devpts is now a separate and equal filesystem.

Reserved ttys are now available to all instances of devpts where the
mounter is in the initial mount namespace.

A new vfs helper path_pts is introduced that finds a directory entry
named "pts" in the directory of the passed in path, and changes the
passed in path to point to it.  The helper path_pts uses a function
path_parent_directory that was factored out of follow_dotdot.

In the implementation of devpts:
 - devpts_mnt is killed as it is no longer meaningful if all mounts of
   devpts are equal.
 - pts_sb_from_inode is replaced by just inode->i_sb as all cached
   inodes in the tty layer are now from the devpts filesystem.
 - devpts_add_ref is rolled into the new function devpts_ptmx.  And the
   unnecessary inode hold is removed.
 - devpts_del_ref is renamed devpts_release and reduced to just a
   deacrivate_super.
 - The newinstance mount option continues to be accepted but is now
   ignored.

In devpts_fs.h definitions for when !CONFIG_UNIX98_PTYS are removed as
they are never used.

Documentation/filesystems/devices.txt is updated to describe the current
situation.

This has been verified to work properly on openwrt-15.05, centos5,
centos6, centos7, debian-6.0.2, debian-7.9, debian-8.2, ubuntu-14.04.3,
ubuntu-15.10, fedora23, magia-5, mint-17.3, opensuse-42.1,
slackware-14.1, gentoo-20151225 (13.0?), archlinux-2015-12-01.  With the
caveat that on centos6 and on slackware-14.1 that there wind up being
two instances of the devpts filesystem mounted on /dev/pts, the lower
copy does not end up getting used.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg KH <greg@kroah.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Peter Anvin <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Serge Hallyn <serge.hallyn@ubuntu.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: Jann Horn <jann@thejh.net>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Florian Weimer <fw@deneb.enyo.de>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

It's an analogue of commit 7500c38a (fix the braino in "namei:
massage lookup_slow() to be usable by lookup_one_len_unlocked()").
The same problem (->lookup()-returned unhashed negative dentry
just might be an autofs one with ->d_manage() that would wait
until the daemon makes it positive) applies in do_last() - we
need to do follow_managed() first.

Fortunately, remaining callers of follow_managed() are OK - only
autofs has that weirdness (negative dentry that does not mean
an instant -ENOENT)) and autofs never has its negative dentries
hashed, so we can't pick one from a dcache lookup.

->d_manage() is a bloody mess ;-/

Cc: stable@vger.kernel.org # v4.6
Spotted-by: NIan Kent <raven@themaw.net>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>